1. Field of the Invention
The present invention relates to a display device which is mounted in the cabin of a working machine for displaying the state and change of the working machine.
2. Related Art
The construction machine is provided in its cabin with a display device for indicating the state of the construction machine such as a cooling water temperature and an abnormality such as a drop in an engine oil pressure. The display device of the prior art will be described with reference to FIG. 8.
On the display screen 81 of a display device 80, there are displayed a state indication mark 82 (in a bar graph) for indicating the state of the construction machine and a state change indication mark 83 for indicating a change having occurred in the working machine. For example, the state indication mark 82 for indicating the temperature of the cooling water of the engine and the residue of the fuel and the caution mark 83 for indicating abnormal values of a battery voltage, an engine oil pressure, a working oil temperature and a cooling water temperature are displayed as bar graphs in the segments of the common display screen 81.
The operator can recognize the fuel residue and the cooling water temperature at present from the displayed content of the state indication mark 82 displayed in the display screen 81 of the display device 80. The operator can further recognize the kind of the prevailing abnormality from the lighting state of the caution mark 83.
In recent years, the construction machine covers multiple functions so that the numbers of the state indication marks 82 and the caution marks 83 to be displayed in the common display screen 81 of the display device 80 are accordingly increased.
In the display device 80 of the prior art, the state indication mark 82 and the caution mark 83 are individually displayed in the independent display segments on the display screen 81.
As the numbers of the state indication marks 82 and the caution marks 83 increase, therefore, the individual mark sizes of the state indication marks 82 and the caution marks 83 have to be reduced so as to display all marks in the limited area of the display screen 81. As the sizes of the individual marks of the state indication marks 82 and the caution marks 83 are reduced, there arises a problem that the visibilities of the individual marks are degraded.
If the increases in the numbers of marks are accommodated with the sizes of the individual marks of the state indication marks 82 and the caution marks 83 being unchanged from those of the prior art, on the contrary, the area of the display screen 81 has to be made larger than that of the prior art. This invites an enlargement of the display device 80.
However, the cabin of the construction machine generally has a limited space to make it unpreferable to enlarge the size of the display device 80.
Thus, the display device 80 of the prior art has a problem that the increase in the number of marks without any enlarged size cannot be performed without lowering the visibilities of the marks.
In Unexamined Published Japanese Patent Application No. 9-78636, on the other hand, there is disclosed an invention, in which the information necessary for controlling the construction machine such as the fuel residue, the cooling water temperature or the engine oil pressure is displayed as the state indication mark on the display screen when no abnormality occurs in the construction machine and in which the state indication mark being displayed is made unindicative but only the caution mark is displayed on the display screen when an abnormality occurs in the construction machine.
Thus, on the display screen, only one of the state indication mark and the caution mark is selectively displayed, but it is unnecessary like the display device 80 of FIG. 8 to display both the state indication mark 82 and the caution mark 83 on the common screen. Even if the number of marks increases, therefore, the individual marks can be arranged without any size reduction in the limited display area thereby to prevent the drop in the visibility.
According to the invention disclosed in Unexamined Published Japanese Patent Application No. 9-78636, however, the state indication mark is made unindicative when an abnormality occurs in the construction machine. From the following reasons, therefore, there arises a problem that the construction machine becomes difficult to drive and control.
By observing the state indication mark the operator can grasp an abnormality to occur in the construction machine at an early stage.
According to the invention of the above-specified Unexamined Publication, when an abnormality occurs in the construction machine, the state indication mark is made unindicative, but only the caution mark is displayed on the display screen. Alternatively, it is possible to alternately repeat the state, in which not the state indication mark but only the caution mark is displayed on the display screen, and the state in which not the caution mark but only the state indication mark is displayed.
In either case, however, there arises a state in which the operator cannot observe the state indication mark. If the state indication mark is made unindicative, therefore, it is impossible to grasp such an abnormality at an early state as will occur in the fuel residue, the cooling water temperature or the engine oil pressure. It is also impossible to grasp an abnormality, if it occurs in the fuel residue, the cooling water temperature or the engine oil pressure, when the caution mark is displayed.
On the other hand, the caution mark is exemplified by the caution mark for indicating, when lit, a heavy abnormality requiring a quick response by stopping the driving control and by the caution mark for indicating, even if lit, a light abnormality not requiring a quick response always. The light abnormality is exemplified by a working oil temperature rise.
Even when the caution mark for indicating the light abnormality is lit and displayed on the display screen, the operator frequently continues the driving control of the construction machine thereby to continue the actions of the running equipment and the working equipment of the construction machine.
When a light abnormality occurs in the construction machine, according to the invention of the Publication, the display screen is switched from the display of the state indication mark to the display of the caution mark like when a heavy abnormality occurs. Therefore, the operator is compelled to continue the driving control with the display screen displaying only the caution mark but not the state indication mark. Of the state indication marks, some display the important information for the driving control which displays working condition such as the running state of the running equipment or the working state of the working equipment. These are the state indication mark for indicating the speed setting (e.g., a high speed (Hi), a medium speed (Mi) and a low speed (Lo)) of the hydraulic motor and the state indication mark for indicating the working mode (e.g., a heavy excavate, an excavate, a calibrate or a fine control) being selected.
Where the state indication mark for indicating the speed setting of the hydraulic motor is not displayed, the operator has to control the running control lever while estimating the speed setting. If the operator controls the running control lever largely by making an erroneous estimation of the “low speed” although the speed setting of the hydraulic motor is at the “high speed” in fact, the crawler may turn at a high speed, contrary to the intention of the operator.
Where the state indication mark for indicating the working mode is not displayed, the operator has to control the control lever for the working equipment while estimating the working mode selected currently. When the operator makes an erroneous estimation of the “fine control” and controls the control lever for the working equipment largely although the working mode selected is the “heavy excavate” in fact so that a high flow rate can be fed to the hydraulic cylinder for the working equipment, the working equipment (e.g., the boom, the arm or the bucket) may largely act at a high speed, although contrary to the intention of the operator.